21664012 has 24 divisors (see below), whose sum is σ = 38707200. Its totient is φ = 10607376.

The previous prime is 21664007. The next prime is 21664037. The reversal of 21664012 is 21046612.

It is a super-2 number, since 2×21664012² = 938658831872288, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 56373 + ... + 56755.

It is an arithmetic number, because the mean of its divisors is an integer number (1612800).

Almost surely, 2^21664012 is an apocalyptic number.

It is an amenable number.

21664012 is a deficient number, since it is larger than the sum of its proper divisors (17043188).

21664012 is a wasteful number, since it uses less digits than its factorization.

21664012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645 (or 643 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21664012 is about 4654.4615155784. The cubic root of 21664012 is about 278.7701673894.

The spelling of 21664012 in words is "twenty-one million, six hundred sixty-four thousand, twelve".